1. Field of Inventions
The present inventions relate generally to surgical probes that support one or more diagnostic or therapeutic elements in contact with body tissue and, more particularly, to surgical probes that support one or more diagnostic or therapeutic elements in contact with bodily orifices and the tissue surrounding such orifices.
2. Description of the Related Art
There are many instances where diagnostic and therapeutic elements must be inserted into the body. One instance involves the treatment of cardiac conditions such as atrial fibrillation and atrial flutter which lead to an unpleasant, irregular heart beat, called arrhythmia.
Normal sinus rhythm of the heart begins with the sinoatrial node (or xe2x80x9cSA nodexe2x80x9d) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or xe2x80x9cAV nodexe2x80x9d). This propagation causes the atria to contract in an organized way to transport blood from the atria to the ventricles, and to provide timed stimulation of the ventricles. The AV node regulates the propagation delay to the atrioventricular bundle (or xe2x80x9cHISxe2x80x9d bundle). This coordination of the electrical activity of the heart causes atrial systole during ventricular diastole. This, in turn, improves the mechanical function of the heart. Atrial fibrillation occurs when anatomical obstacles in the heart disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called xe2x80x9cconduction blocksxe2x80x9d) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called xe2x80x9creentry circuits,xe2x80x9d disrupt the normally uniform activation of the left and right atria.
Because of a loss of atrioventricular synchrony, the people who suffer from atrial fibrillation and flutter also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are also at greater risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
One surgical method of treating atrial fibrillation by interrupting pathways for reentry circuits is the so-called xe2x80x9cmaze procedurexe2x80x9d which relies on a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits. The maze procedure has been found very effective in curing atrial fibrillation. However, the maze procedure is technically difficult to do.
Maze-like procedures have also been developed utilizing catheters which can form lesions on the endocardium (the lesions being 1 to 15 cm in length and of varying shape) to effectively create a maze for electrical conduction in a predetermined path. The formation of these lesions by soft tissue coagulation (also referred to as xe2x80x9cablationxe2x80x9d) can provide the same therapeutic benefits that the complex incision patterns that the surgical maze procedure presently provides.
Catheters used to create lesions typically include a relatively long and relatively flexible body portion that has a soft tissue coagulation electrode on its distal end and/or a series of spaced tissue coagulation electrodes near the distal end. The proximal end of the flexible body is typically connected to a handle which includes steering controls. The portion of the catheter body portion that is inserted into the patient is typically from 23 to 55 inches in length and there may be another 8 to 15 inches, including a handle, outside the patient. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the interior of the heart, and then manipulated such that the coagulation electrode contacts the tissue that is to be ablated. Linear and curvilinear lesions can then be created by dragging a single electrode or by applying power (preferably simultaneously) to the series of spaced electrodes.
Catheter-based soft tissue coagulation has proven to be a significant advance in the medical arts generally and in the treatment of cardiac conditions in particular. Nevertheless, the inventors herein have determined that catheter-based procedures are not appropriate in every situation and that conventional catheters are not capable of reliably forming all types of lesions. For example, one lesion that has proven to be difficult to form with conventional catheter devices is the circumferential lesion that is used to isolate the pulmonary vein and cure ectopic atrial fibrillation. Lesions that isolate the pulmonary vein may be formed within the pulmonary vein itself or in the tissue surrounding the pulmonary vein. These circumferential lesions are formed by dragging a tip electrode around the pulmonary vein or by creating a group of interconnected curvilinear lesions one-by-one around the pulmonary vein. Such techniques have proven to be less than effective because they are slow and gaps of conductive tissue can remain after the procedure. It can also be difficult to achieve the adequate tissue contact with conventional catheters.
Accordingly, the inventors herein have determined that a need exists for structures that can be used to create circumferential lesions within or around bodily orifices and, in the context of the treatment of atrial fibrillation, within or around the pulmonary vein.
Accordingly, the general object of the present inventions is to provide a device that avoids, for practical purposes, the aforementioned problems. In particular, one object of the present inventions is to provide a device that can be used to create circumferential lesions in or around the pulmonary vein and other bodily orifices in a more efficient manner than conventional apparatus.
In order to accomplish some of these and other objectives, a surgical probe in accordance with one embodiment of a present invention includes a relatively short shaft, a support structure associated with the distal end of the relatively short shaft, and an operative element supported on the support structure. The support structure in one preferred implementation includes a loop-like portion that supports the operative element, such as a plurality of electrodes, in a plane that is perpendicular to the longitudinal axis of the shaft. The support structure is also preferably bendable.
Such a probe provides a number of advantages over conventional apparatus. For example, the present surgical probe may be used during open heart surgery or in less invasive procedures where access to the heart is obtained via a thoracostomy, thoracotomy or median sternotomy. The relatively short shaft and manner in which access is obtained allows the electrodes to be easily inserted into the heart and placed against the target tissue with the desired level of contact, thereby eliminating many of the problems associated with catheter-based procedures. The loop-like portion can be used to position the electrodes within or around the pulmonary vein (or other orifice in other procedures) so that a circumferential lesion can be created in one step. In addition, the flexibility of the support structure allows the physician to achieve the appropriate level of tissue contact, even when the shaft is not perfectly perpendicular to the target tissue area and when the target tissue area is somewhat uneven.
In order to accomplish some of these and other objectives, a surgical probe in accordance with one embodiment of a present invention includes a relatively short shaft, a support structure, an operative element supported on the support structure, and an anchor member associated with at least one of the relatively short shaft and the support structure and extending distally therefrom. Such a probe provides a number of advantages over conventional apparatus. For example, the anchor member can be inserted into a bodily orifice such as the pulmonary vein in order accurately position the operative element relative to the orifice. In a preferred implementation, the support structure includes a loop-like portion that supports a plurality of electrodes. Here, the anchor member can be used to center the loop-like portion and electrodes with respect to the pulmonary vein or other bodily orifice so that a circumferential lesion can be quickly and accurately formed in or around the pulmonary vein or other bodily orifice.
The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.